A number of studies have provided evidence that human fertility has declined over recent decades, raising alarm that a widespread reproductive toxicant exists in the environment. We carried out simulations to assess the bias due to recent trends in the availability of effective methods of birth control, including induced abortion, and showed that contradictory reports in the literature can potentially be explained by demography-induced biases, and that the study of trends in fertility is particularly susceptible to bias and misinterpretation.